In the presence of Zn/Cp^2 TiCl^2(cat.) α -bromoacetates, γ-bromocrotonates or α-bromomethylacrylates react with imines in one-pot to form β-lactams, 3-vinyl-β-lactms or α-methylene-γ-lactams, respectively, at room temperature without the need for pretreatment of the solvent and Zn.